Tom Cruise threw the first grenade in the bust-up of his marriage to Nicole Kidman yesterday – officially filing for divorce against the sexy redhead actress.

The Hollywood power couple stunned movie fans this week by announcing their separation, but in a stinging divorce petition filed in Los Angeles Superior Court, Cruise revealed they’ve actually been apart since December.

Cruise cited “irreconcilable differences” for the breakup and asked a judge to grant joint custody of their two adopted kids – Isabella, 8, and Connor, 6.

He asked the court to throw out any request Kidman might make for support and wants a fair split of assets.

His legal missile sets the stage for what could be an ugly divorce battle with hundreds of millions of dollars hanging in the balance.

Cruise, 38, is said to be worth at least $225 million, while Kidman, 33, reportedly has around $110 million in the bank.

Cruise has been married to Kidman since Dec. 24, 1990, and this marks his second failed marriage. He previously split from actress Mimi Rogers in 1990.